The presence of essential metals sometimes referred to as trace minerals, in sufficient quantities and in a biologically available form in diet is necessary for maintaining the health and well-being of domestic animals and poultry. Because essential metals such as copper, iron, manganese and zinc are often deficient in common feed ingredients, supplemental amounts of these nutrients are often added to the feed of domesticated animals and poultry. Many commercial feed additives have been developed to provide the essential metals in forms that are readily biologically utilizable. The degree of biological availability of nutrients is often referred to as “bioavailability”. Bioavailability of essential metals depends on the physical and/or chemical properties of the form in which the metal is present in the diet. Increased bioavailability of supplemental metals is beneficial because it allows the use of lower concentrations of the metals in the diet to meet the nutritional needs of animals, while lowering the potential harmful effects of high levels of these metals both on the animals and on the environment.
Several commercial products are available in which trace elements are more bioavailable than the corresponding inorganic source of the metal. The enhanced bioavailability is attributed to the association of the metal with an organic molecule, generally known as a ligand. This association or bonding results in the increased availability of the metal for utilization by animals, i.e. increased bioavailability. The increased bioavailability of the essential elements in these products is the result of increased solubility, greater stability in the gut, enhanced absorption into circulation and/or improved metabolic utilization.
Different types of products that contain a trace element associated with an organic ligand are commercially available. These can be classified in different groups based on the nature of the ligand used in manufacturing the product. In one class of products, amino acids are used as the ligands that form complexes or chelates with the metal. Examples of these products are described in U.S. Pat. Nos. 3,941,818; 3,950,372; 4,067,994; 4,863,898 4,900,561; 4,948,594; 4,956,188; 5,061,815; 5,278,329; 5,583,243; and 6,166,071. A second group of feed additives include the metal salts of short chain carboxylic acids such as propionic acid (See U.S. Pat. Nos. 5,591,878, 5,707,679, 5,795,615 and 5,846,581). A third group of trace element additives is classified by the American Feed Control Officials as Metal Proteinate and defined as “the product resulting from the chelation of a soluble salt with amino acids and/or partially hydrolyzed protein”. Examples of these products are described in U.S. Pat. Nos. 3,440,054, 3,463,858, 3,775,132, 3,969,540, 4,020,158, 4,076,803, 4,103,003, 4,172,072 and 5,698,724.
The common assignee of the present application has in the past synthesized and patented metal complexes of amino acids as a more bioavailable source of the essential elements. The following are examples of these patents: U.S. Pat. Nos. 3,941,818; 3,950,372; 4,021,569; 4,039,681; and 4,067,994 disclose 1:1 complexes of alpha amino acids, preferably DL-methionine with the transition metals zinc, chromium, manganese and iron. The formation of similar complexes with L-methionine is disclosed in U.S. Pat. No. 5,278,329. U.S. Pat. Nos. 4,900,561 and 4,948,594 disclose copper complexes of alpha amino acids containing terminal amino groups. Complexes of copper, manganese, zinc and iron with alpha hydroxyl aliphatic carboxylic acids are disclosed in U.S. Pat. Nos. 4,956,188 and 5,583,243. U.S. Pat. Nos. 4,670,269 and 4,678,854 disclose complexes of cobalt with poly-hydroxy carboxylic acid such as glucoheptanoic acid. Complexes of the amino acid L-lysine with trace elements are disclosed in U.S. Pat. No. 5,061,815. The effectiveness of the compounds disclosed in these patents has been demonstrated from data provided in some of these patents and in numerous scientific publications and technical reports.
The above patents describe the use of pure synthetic or natural amino acids. In U.S. Pat. No. 5,698,724 the assignee of the current application disclosed the synthesis of complexes of essential elements with natural amino acids obtained by the hydrolysis of proteins. Since this patent was issued, a large number of field studies have demonstrated that metals from these complexes are more bioavailable than metals from inorganic sources.
Ethylene diamine (EDA) is well known in the chemistry arena and is a building block for many compounds and polymers. It is also an important ligand for metal complexation. As such, it has been chemically modified to produce one of the best and well known chelating agents, EDTA (ethylenediame tetracetic acid). Finding a good ligand for chemical complexation of metals is completely different than finding a good ligand for nutritional delivery of the metal to animals for animal performance. There are many factors that determine if a ligand will be effective for delivery of a mineral to an animal. Often it can be difficult to evaluate the effectiveness of a given metal ligand since inorganic mineral is a nutritionally viable source of mineral. Many factors determine if organic metal sources are suitable to provide a bioavailable source of trace minerals. A good carrier for the trace mineral must be an organic molecule which provides solubility at physiological conditions, stability in stomach acid; it must be able to be absorbed intact through the intestinal wall, and it must release the trace mineral to the animal body for use, rather than excrete it.
The increased performance or efficacy of an organic trace mineral must be determined by careful selection of the study so as to be sure you are identifying a performance response versus a mineral response. Comparison of the same metal levels versus an inorganic control is typically required. Absorption of the metal-ligand complex intact is required to be considered an organic trace mineral. If disassociation occurs before absorption one would not expect performance differences from inorganic minerals.
With all this in mind an effective organic trace mineral must be soluble and stable at physiological conditions and the mineral must be absorbed intact. Common ligands that have been used in the area of animal nutrition are propionic acid, amino acids, hydroxy acids, proteinates, etc.
Accordingly, it is a primary objective of the present invention to provide a preferred small molecule ligand of the metals copper, iron, zinc and manganese in a format which is highly absorbable, soluble at physiological conditions, stable in stomach acid, absorbed intact and able to release the mineral to the animal rather than excrete it.
Another objective of the present invention is to provide the above metal ligands in an easily processable form, and one that is easy to make, and easy to use for supplementation.
The method and manner of accomplishing the above objectives as well as others will become apparent from the detailed description of the invention.